Enhanced Mechanism of Buffer Status Reporting to Multiple Schedulers in a Wireless Network

ABSTRACT

Apparatus and method are provided to enhance buffer status report (BSR) to multiple schedulers with inter base station carrier aggregation. In one novel aspect, the UE calculates a buffer size value, detects a BSR trigger event, selects one or more base stations (BSs) to send the BSR reports and generates the BSR reports for the selected one or more BSs. In one embodiment, one BS is selected based on predefined criteria. In other embodiments, multiple base stations are selected. In one embodiment, the same contents for BSR are generated. In another embodiment, different BSR reports are generated for different base stations from which the UE receives UL grants. In one novel aspect, the UE calculates a buffer size value and determines if a budget BSR triggering criteria is satisfied. The UE triggers budget BSR procedure by sending a budget BSR report to a selected base station based on predefined thresholds.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation, and claims priority under 35 U.S.C.§120 from nonprovisional U.S. patent application Ser. No. 14/804,461,entitled “Enhanced Mechanism of Uplink Time Alignment Maintenance forInter-eNB Carrier Aggregation”, filed on Jul. 21, 2015, the subjectmatter of which is incorporated herein by reference. application Ser.No. 14/804,461, in turn, is a continuation, and claims priority under 35U.S.C. §120 and §365(c) from International Application No.PCT/CN2014/077650, with an international filing date of May 16, 2014,which in turn claims priority from CN Application NumberCN201310184746.8, entitled “Enhanced Mechanism of Buffer StatusReporting to Multiple Schedulers in a Wireless network with Inter BaseStation Carrier Aggregation” filed on May 17, 2013. This applicationclaims the benefit under 35 U.S.C. §119 from Chinese ApplicationCN201310184746.8. The disclosure of each of the foregoing documents isincorporated herein by reference.

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless communicationsystems, and, more particularly, to enhanced mechanism of Buffer StatusReport reporting to multiple schedulers with inter-base station carrieraggregation.

BACKGROUND

A Long-Term Evolution (LTE) system offers high peak data rates, lowlatency, improved system capacity, and low operating cost resulting fromsimplified network architecture. LTE systems also provide seamlessintegration to older wireless network, such as GSM, CDMA and UniversalMobile Telecommunication System (UMTS). In LTE systems, an evolveduniversal terrestrial radio access network (E-UTRAN) includes aplurality of base stations, e.g., evolved Node-Bs (eNBs) communicatingwith a plurality of mobile stations referred as user equipments (UEs).

A Buffer status report (BSR) is sent from the UE to the serving eNB toprovide information about the amount of pending data in the uplinkbuffer of the UE. The buffer status, along with other information, suchas priorities allocated to different logical channels, is useful for theuplink scheduling process to determine which UEs or logical channelsshould be granted radio resources at a given time. The UE communicatesthe BSR to the scheduler in the base station so that the base stationhas sufficient information about the data waiting in the UE for ULtransmission. The base station can allocate appropriate UL resource forthe UE in a timely manner. Traditionally, the UE reports the bufferstatus to only one base station, which is its serving base station. Thismethod encounters problem with the use of inter-base station carrieraggregation.

Carrier aggregation (CA) is introduced to improve system throughput.With carrier aggregation, the LTE-Advance system can support higher datarate. Such technology is attractive because it allows operators toaggregate several smaller contiguous or non-continuous componentcarriers (CC) to provide a larger system bandwidth, and providesbackward compatibility by allowing legacy users to access the system byusing one of the component carriers. LTE also allows carrier aggregationfrom different eNBs or from different radio access technology (RAT).Different from the traditional wireless system, with inter-eNB orinter-RAT carrier aggregation, the UE needs to associate with multipleschedulers from different base stations. For inter-BS carrieraggregation, the base stations providing the carrier components are notphysically collocated, it requires transmission medium and interfacesamong the base stations. Therefore, the UE has to provide separate BSRsto different schedulers residing in different base stations.

Improvements and enhancements are required for UE BSR procedures tocommunicate and manage multiple schedulers from different base stations.

SUMMARY

Apparatus and method are provided to enhance buffer status report (BSR)to multiple schedulers with inter base station carrier aggregation. Inone novel aspect, the UE calculates a buffer size value, detects a BSRtrigger event. The UE selects one or more base stations (BSs) to sendthe BSR reports and generates the BSR reports for the selected one ormore BSs. In one embodiment, one BS is selected based on predefinedcriteria. In other embodiments, multiple base stations are selected toreceive BSR reports. In one embodiment, the same contents for BSR aregenerated for all base stations from which the UE receives UL grants. Inanother embodiment, different BSR reports are generated for differentbase stations from which the UE receives UL grants.

In one novel aspect, a budget BSR procedure is triggered upon detectingone or more predefined budget BSR triggering events. In one embodiment,the UE calculates a buffer size value. The UE determines if a budget BSRtriggering criteria is satisfied. The UE triggers budget BSR procedureby sending a budget BSR report to a selected base station based onpredefined thresholds.

Other embodiments and advantages are described in the detaileddescription below. This summary does not purport to define theinvention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components,illustrate embodiments of the invention.

FIG. 1 illustrates a system diagram of a wireless network with inter-eNBor inter-RAT carrier aggregation in accordance with one novel aspect.

FIG. 2 is an exemplary flow diagram of a UE transmitting one or moreBSRs to different base station in accordance with embodiments of thecurrent invention.

FIG. 3 is an exemplary diagram of a UE transmitting BSR reports todifferent base stations.

FIG. 4 is an exemplary flow diagram of a UE transmitting one or moreBSRs to different base station in accordance with embodiments of thecurrent invention.

FIG. 5 is a schematic diagram of a UE transmitting BSR to multiple basestations by joint BSR in accordance with embodiments of the invention.

FIG. 6 is a schematic diagram of a UE transmitting BSR to multiple basestations by separate BSR in accordance with embodiments of theinvention.

FIG. 7 is a flow diagram of a UE transmitting BSR to multiple basestations using separate or joint BSR.

FIG. 8 is a schematic diagram of a UE transmitting BSR to multiple basestations by hybrid BSR in accordance with embodiments of the invention.

FIG. 9 is a flow diagram of a UE transmitting BSR to multiple basestations using hybrid BSR.

FIG. 10 is an exemplary flow diagram of a UE calculating the bufferstatus value for BSR in accordance with embodiments of the currentinvention.

FIG. 11 is an exemplary flow diagram of a UE calculating buffer statusvalue for separate BSRs to different base stations with the samecontents.

FIG. 12 is an exemplary flow diagram of a UE calculating buffer statusvalue for separate BSRs to different base stations with the differentcontents.

FIG. 13 is an exemplary flow diagram of a UE providing BSR and BudgetBSR to different base stations with separate MAC entities based on BSRand Budget BSR triggering and reporting.

FIG. 14 is an exemplary flow diagram of a UE triggering a Budget BSR inaccordance with embodiments of the invention.

FIG. 15 is an exemplary flow diagram of a UE sending ano-data-indication to one or more base stations in accordance withembodiments of the current invention.

FIG. 16 is a flow diagram of a UE selecting one or more base station tosend one or more BSR reports in accordance with embodiments of thecurrent invention.

FIG. 17 is a flow diagram of a UE performs Budget BSR procedure inaccordance with embodiments of the current invention.

FIG. 18 is an exemplary flow diagram of a UE transmitting BSRs todifferent BSs implementing avoidance of radio resource over-allocation.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings.

FIG. 1 illustrates a system diagram of a wireless network 100 withinter-eNB or inter-RAT carrier aggregation in accordance with one novelaspect. Wireless network 100 comprises a main base station eNB, alsoreferred as an anchor eNB 102, two drift eNBs 103 and 104 and a UE 101.Wireless network 100 supports multiple component carriers over differentfrequency channels, and carrier aggregation for serving cells originatedfrom different eNBs. For uplink (UL) synchronization between a UE andits base station with respect to each component carrier (CC), the UEreceives an UL timing advance from the eNB, which compensates for thepropagation delay between the eNB and the UE. Since UE 101 can be servedwith radio resources from eNB 102, eNB 103 and eNB 104, it may need tosend BSR to one or more of the serving cells in wireless 100. Wirelessnetwork 100 can be an inter-RAT CA network, with the anchor eNB 102employs one technology, for example LTE or other cellular standards,while drift eNBs 103 and 104 using different wireless standards, such asWifi. Regardless of the inter-BS CA using the same standard or differentstandard, UE 101 is configured to associate with different schedulers ineach of the base stations, eNB 102, eNB 103 and eNB 104. Upon detectinga BSR triggering event, UE 101 needs to decide to which base station theBSR should be sent. The UE also need to decide how to build the one ormore BSRs.

In one exemplary configuration, wireless network 100 is a small cellnetwork. Initially, UE 101 camps on the macro cell served by eNB 102. UE101 establishes Radio Resource Control (RRC) connection with the RadioAccess Network (RAN). eNB 102 provides and controls the initial RRCconnection and provides NAS mobility information and security input. eNB102 is the anchor eNB for UE 101. In a small cell network configuration,UE 101 moves within the coverage area of anchor eNB 102 while movinginto the coverage area of eNB 103. Upon entering eNB 103 coverage area,UE 101 can offload some traffic to eNB 103 if needed. In such situation,inter-eNB carrier aggregation can be configured for UE 101. UE 101 canuse additional resources from eNB 103, which is a drift eNB in the smallcell network system. The coordination between anchor eNB 102 and drifteNB 103 can be performed through Xn interface, for example, X3 or X2interface. The Xn interfaces, also known as backhaul connections providecommunication and coordination between eNBs. However, heavy reliance onsuch interface introduces undesirable delays for the system.

FIG. 1 also includes simplified block diagrams of protocol stacks insmall cell network 100 for anchor eNB 102, drift eNB 103 and UE 101. Atnetwork side, the protocol stack in anchor eNB 102 includes PHY, MAC,RLC, PDCP, RRC, and a scheduler. Because drift eNB 103 has its ownindependent scheduler, the protocol stack in eNB 103 includes at leastPHY, MAC, and a scheduler, and possible RLC too. At UE side, for UEsequipped with multiple PHY and MAC modules, they can be configured basedon its usage for carrier aggregation and small cell operation. In onenovel aspect of the current invention, UE 101 has multiple RLC layerswith corresponding MAC layers associated with corresponding PHY layer.In one embodiment, UE 101 is equipped with RLC1 corresponding to MAC1and established RRC connection with anchor eNB 102. As UE 101 moves intothe coverage area of eNB 103, the network may decide to aggregationresources from eNB 103 to offload traffics from UE 101. Therefore, UE101 is also configured with RLC2 corresponding to MAC2, and thecorresponding PHY sub-layer, which is PHY2.

FIG. 2 is a schematic diagram of a wireless network 200 that supportsinter-eNB carrier aggregation with different cell groups configured fora UE 201 in accordance with embodiments of the current invention. UE 201establishes RRC connection with anchor eNB 202. Network 200 supportsinter-eNB or inter-RAT carrier aggregation. UE 201 is configured withinter-eNB carrier aggregation. When UE 201 moves into the coverage areaof eNB 203, UE 201 can be configured with inter-eNB carrier aggregation.UE 201 can offload traffic from eNB 202 to eNB 203. UE 201 can beconfigured with multiple serving cells originated from two differenteNBs, for example eNB 202 and eNB 203. UE 201 is configured withmultiple LCs, for example, LC #1 to LC #5. UE 201 is also configuredwith multiple logical channel groups (LCGs). LC #1 is configured for UE201 and is associated with eNB 202. Similarly, LC #2 is associated witheNB 202, and LC #5 is associated with eNB 203. LC #3 is configured to beable to associate with eNB 202 or eNB 203. Similarly, LC #5 isconfigured to be able to associate with eNB 202 and eNB 203. MultipleLCGs are configured for UE 201. LCG #1 contains LC #1, LC #2 and LC #3.LCG #2 contains LC #4 and LC #5. Such configuration gives UE 201 largerbandwidth and more flexibility in aggregating resource but it poses aset of UL resource management issues. For example, upon detecting a BSRtriggering event, the UE has to decide how to which eNB or eNBs the BSRreports should be sent. The UE also need to decide how to build the oneor more BSR reports for each selected eNB.

FIG. 2 also includes a simplified block diagram of UE 201 in accordancewith novel aspects of the current invention. UE 201 comprises memory211, a processor 212, a transceiver 213 coupled to an antenna 218. UE201 also comprises various function modules including a calculatingmodule 221, a configuration module 222, a BSR detection module 223, anUL scheduler selection module 224, one or BSR generation modules 225, afirst MAC entity module 226, a second MAC entity module 227 and a budgetBSR module 228. Calculating module 221 calculates a buffer status value,which can be used to build the BSR reports to be sent to one or moreselected base stations. Configuration module 222 configures LCs of UE201 to one or more LCGs accordingly. Configuration module 222 configuresLCs either binding to a specific base station via a specific MAC entity,or configures LCs to no specific base stations. BSR detection module 223monitors and detects BSR triggering events. UL scheduler selectionmodule 224, upon receiving BSR triggering events, selects one or more ULschedulers to send the BSR based on predefined algorithms. BSRgeneration module 225 generates BSR reports to be sent to the selectedone or more UL schedulers. UE 201 may have one or more BSR generationmodules. In one embodiment, each MAC entity has its own BSR generationmodule handling BSR report to its corresponding scheduler. In anotherembodiment, UE 201 has one BSR generation module for all MAC entities.In yet another embodiment, UE 201 has one BSR generation handling a setof predefined BSR triggers for all MAC entities, and other BSRgeneration modules for each MAC entity for a different set of predefinedBSR triggers. First MAC entity 226 communicates with a first basestation. Second MAC entity 227 communicates with a second base station.It is understood by one with ordinary skills in the art that more thantwo MAC entities can be included in UE 201 when configured. Budget BSRmodule 228 processes budget BSR according to predefined algorithms.

FIG. 3 is an exemplary diagram of a UE 301 transmitting BSR reports todifferent base stations. UE 301 communicates with base station BS 302and base station BS 303. BS 302 and BS 303 allocate UL resources for UE301. UE 301 sends BSR reports to BS 302 and/or BS 303. In onetransmission time interval (TTI), if UE 301 only receives one UL grantfrom BS 302 or BS 303, UE 301 transmits one BSR report to one of thebase stations. If UE 301 receives multiple UL grants in one TTI, UE 301may transmit multiple BSRs to the base station. UE 301 has multiplelogical channels (LC), LC#1 to LC#9, divided into a plurality of logicalchannel groups (LCGs), LCG 311, 312, 313 and 314. Each LCG has one ormore LCs, or no LC. As an example shown in FIG. 3, LCG 311 has four LCs,LC#1, LC#2, LC#3 and LC#4. LCG 312 has one LC, LC#5. LCG 313 has twoLCs, LC#6 and LC#7. LCG 314 has two LCs, LC#8 and LC#9. Each LCG has acorresponding LCG buffer. LCG 311 has LCG#1 buffer 321. LCG 312 hasLCG#2 buffer 322. LCG 313 has LCG#3 buffer 323. LCG 314 has LCG#4 buffer324. Further, each LCG buffer has a corresponding buffer status. LCGbuffer 321 has LCG#1-buffer status 331. LCG buffer 322 has LCG#2-bufferstatus 332. LCG buffer 323 has LCG#3-buffer status 333. LCG buffer 324has LCG#4-buffer status 334.

Due to inter-base station carrier aggregation, UE 301 may receivemultiple UL grants from one or multiple base stations. If UE 301receives multiple UL grants from one base station in one TTI, either BS302 or BS 303, each LCG shall report at most one BSR value per TTI tothe BS. This buffer status value shall be reported in BSR associatedwith this LCG. If UE 301 receives multiple UL grants by both BS 302 andBS 303 in one TTI, UE 301 can transmit multiple BSRs to either one BS ormultiple BSs. Each LCG can report the same buffer status value to allBSs or report different buffer status values to different BSs. Thougheach LCG can report different buffer status values to different BSs, UE301 can only report one buffer status value per TTI to the same BS andthis value shall be reported in all BSRs for this LCG.

UE 301 monitors and detects BSR trigger events. At step 341, UE 301sends a BSR to BS 302. At step 342, BS 302 replies to UE 301 with ULgrants. At step 343, UE 301 sends a BSR to BS 303. At step 344, BS 303replies to UE 301 with UL grants.

FIG. 4 is an exemplary flow diagram of a UE transmitting one or moreBSRs to different base station in accordance with embodiments of thecurrent invention. At step 401, the UE monitors layer two buffers. Atstep 402, the UE detects predefined conditions. At step 403, the UEdetects one or more BSR trigger events. At step 404, the UE waits forone or more UL grants indications. At step 405, the UE checks if atleast one UL grant is received. If step 405 determines that no UL grantis received, the UE goes back to step 402 to detect predefinedconditions. If step 405 determines that one or more UL grants arereceived, the UE moves to step 406. At step 406, the UE restart the BSRretransmission timer. At step 407, the UE checks if all the BSR triggersare cancelled. If step 407 finds that all BSR triggers are cancelled,the UE goes back to step 402 to detect predefined conditions. If step407 finds that there are one or more BSR triggers not cancelled, the UEmoves to step 408. At step 408, the UE calculates the available space oftransmitting protocol data units (PDUs). At step 409, the UE determinesif the available space of transmitting PDUs has enough space for BSR. Atstep 410, the UE finds the PDUs that have enough for BSR. At step 411,the UE determines if it finds the PDU that met the requirements. If step411 determines the UE cannot find the required PDUs, it moves to step412. At step 412, the UE determines if the UL grants can hold all data.If step 412 determines that the UL grants can hold all data, the UEmoves to step 420, which cancels BSR and end the procedure. If step 412determines that the UL grants cannot hold all data, the UE moves back tostep 402 to detect predefined conditions. If step 411 finds requiredPDU, the UE moves step 413. At step 413, the UE calculates a bufferstatus value for the BSR reporting. At step 414, the UE selects the PDUsthat would contain the BSR. At step 415, the UE instructs multiplexingand assembly process to generate a BSR. At step 416, the UE determinesif the generated BSR can provide full buffer status information. If step416 determines yes, the UE moves step 417 and starts or restarts the BSRperiodic timer. If step 416 determines no, the UE moves to step 418 andstarts or restarts the BSR retransmission timer. At step 419, the UEcommunicates the generated BSR to the BS. At step 420, the UE cancelsBSR and ends the procedure.

To handle inter-base station carrier aggregation, multiple MAC entitiesare configured for a UE. In general, each MAC entity in the UEcorresponds to a base station that the UE is associated. In oneembodiment, the BSR functions are performed independent of MAC entities.The UE has one BSR functional block that controls each MAC entity forthe BSR procedure. In another embodiment, each MAC entity has its ownfunction entity for the BSR procedure. In yet another embodiment, the UEhas hybrid BSR entities. The UE is configured with an independent BSRentity handling one set of predefined BSR trigger events. At the sametime, each MAC entity of the UE also has its own BSR entity handling aseparate set of BSR trigger events. The following section describes theabove embodiments in details.

Joint BSR

FIG. 5 is a schematic diagram of a UE 501 transmitting BSRs to multiplebase stations by joint BSR in accordance with embodiments of theinvention. UE 501 communicates with base station BS 502 and base stationBS 503. BS 502 and BS 503 allocate UL resources for UE 501. UE 501 sendsBSR reports to BS 502 and/or BS 503. UE 501 has multiple logicalchannels (LC), LC#1 to LC#9, divided into a plurality of logical channelgroups (LCGs), LCG 511, 512, 513 and 514. Each LCG has one or more LCs,or no LC. As an example shown in FIG. 5, LCG 511 has four LCs, LC#1,LC#2, LC#3 and LC#4. LCG 512 has one LC, LC#5. LCG 513 has two LCs, LC#6and LC#7. LCG 514 has two LCs, LC#8 and LC#9. Each LCG has acorresponding LCG buffer. LCG 511 has LCG#1 buffer 521. LCG 512 hasLCG#2 buffer 522. LCG 513 has LCG#3 buffer 523. LCG 514 has LCG#4 buffer524. Further, each LCG buffer has a corresponding buffer status. LCGbuffer 521 has LCG#1-buffer status 531. LCG buffer 522 has LCG#2-bufferstatus 532. LCG buffer 523 has LCG#3-buffer status 533. LCG buffer 524has LCG#4-buffer status 534. An independent function entity for BSRhandling 541 of UE 501 handles BSR procedures for UE 501. BSR handler541 controls a MAC entity 551 and a MAC entity 552, which are associatedto BS 502 and BS 503, respectively. It is understood by one of ordinaryskills in the art that more two MAC entities can be configured tocommunicate with multiple base stations. BSR handler 541 controls themultiple MAC entities in similar manners.

In the joint BSR configuration, a periodic timer(periodicBSR-Timer), anda retransmission timer(retxBSR-Timer) is used by BSR handler 541 tocontrol the BSR reporting behavior and to avoiding the dead lock. If theUL resources allocated for new transmission are granted from any BS, theBSRs triggered by BSR handler 541 are considered. If the UL grants inthe current subframe can accommodate all pending data available fortransmission but is not sufficient to accommodate the BSRs, alltriggered BSR by BSR handler 541 shall be cancelled. UE 501 monitors anddetects BSR trigger events. If BSR handler 541 determines BSR reportingis needed, at step 561, UE 501 sends a BSR to BS 502. At step 562, BS502 replies to UE 501 with UL grants. At step 563, UE 501 sends a BSR toBS 503. At step 564, BS 503 replies to UE 501 with UL grants.

Separate BSR

FIG. 6 is a schematic diagram of a UE 601 transmitting BSRs to multiplebase stations by separate BSR in accordance with embodiments of theinvention. UE 601 communicates with base station BS 602 and base stationBS 603. BS 602 and BS 603 allocate UL resources for UE 601. UE 601 sendsBSR reports to BS 602 and/or BS 603. UE 601 has multiple logicalchannels (LC), LC#1 to LC#9, divided into a plurality of logical channelgroups (LCGs), LCG 611, 612, 613 and 614. Each LCG has one or more LCs,or no LC. As an example shown in FIG. 6, LCG 611 has four LCs, LC#1,LC#2, LC#3 and LC#4. LCG 612 has one LC, LC#5. LCG 613 has two LCs, LC#6and LC#7. LCG 614 has two LCs, LC#8 and LC#9. Each LCG has acorresponding LCG buffer. LCG 611 has LCG#1 buffer 621. LCG 612 hasLCG#2 buffer 622. LCG 613 has LCG#3 buffer 623. LCG 614 has LCG#4 buffer624. Further, each LCG buffer has a corresponding buffer status. LCGbuffer 621 has LCG#1-buffer status 631. LCG buffer 622 has LCG#2-bufferstatus 632. LCG buffer 623 has LCG#3-buffer status 633. LCG buffer 624has LCG#4-buffer status 634. A MAC entity 651 and a MAC entity 652communicate with BS 602 and BS 603, respectively. MAC entity 651 and MACentity 652 also have their own BSR handling functions. It is understoodby one of ordinary skills in the art that more two MAC entities can beconfigured to communicate with multiple base stations. Each of themultiple MAC entities has similar functions as MAC entity 651 and MACentity 652.

In the separate BSR configuration, a periodic timer(periodicBSR-Timer),and a retransmission timer(retxBSR-Timer) is used by MAC entity 651 andMAC 652 to control the BSR reporting behavior, for example, to avoid thedead lock. If the UL resources allocated for new transmission aregranted from any BS, each MAC entity checks its corresponding BSRs todetermine whether the triggered BSRs should be cancelled. If the ULgrants in the current subframe can accommodate all pending dataavailable for transmission but is not sufficient to accommodate theBSRs, the BSRs triggered by the corresponding MAC entity should becancelled while the BSRs triggered by other MAC entities should not beaffected. UE 601 monitors and detects BSR trigger events. If MAC entity651 determines BSR reporting is needed, at step 661, UE 601 sends a BSRto BS 602. At step 662, BS 602 replies to UE 601 with UL grants. If MACentity 652 determines BSR reporting is needed, at step 663, UE 601 sendsa BSR to BS 603. At step 664, BS 603 replies to UE 601 with UL grants.

When the UE is configured with either joint BSR or separate BSR, a BSRshall be triggered either by the independent BSR handler, such as BSRhandler 541, or by BSR functions in each MAC entity, such as MAC entity651 or MAC entity 652. The UE triggers the BSR process when anypredefined condition is detected. The predefined conditions may includethe arrival of higher priority data, the expiration of the BSRretransmission timer, the expiration of the BSR periodic timer andpadding spaces being available to accommodate the BSR.

FIG. 7 is a flow diagram of a UE transmitting BSR to multiple basestations using separate or joint BSR. At step 701, the UE determines ifhigh priority data arrived. If step 701 determines yes, the UE moves tostep 711 to set the BSR trigger. If step 701 determines no, the UE movesto step 702. At step 702, the UE determines if the BSR retransmissiontimer expired. If step 702 determines yes, the UE moves to step 711 toset the BSR trigger. If step 702 determines no, the UE moves to step703. At step 703, the UE determines if the BSR periodic timer expired.If step 703 determines yes, the UE moves to step 711 to set the BSRtrigger. If step 703 determines no, the UE moves to step 704. At step704, the UE determines is there is padding space available toaccommodate the BSR. If step 704 determines yes, the UE moves to step711 to set the BSR trigger. If step 704 determines no, the UE terminatesthe procedure.

Hybrid BSR

FIG. 8 is a schematic diagram of a UE 801 transmitting BSR to multiplebase stations by hybrid BSR in accordance with embodiments of theinvention. UE 801 communicates with base station BS 802 and base stationBS 803. BS 802 and BS 803 allocate UL resources for UE 801. UE 801 sendsBSR reports to BS 802 and/or BS 803. UE 801 has multiple logicalchannels (LC), LC#1 to LC#9, divided into a plurality of logical channelgroups (LCGs), LCG 811, 812, 813 and 814. Each LCG has one or more LCs,or no LC. As an example shown in FIG. 8, LCG 811 has four LCs, LC#1,LC#2, LC#3 and LC#4. LCG 812 has one LC, LC#5. LCG 813 has two LCs, LC#6and LC#7. LCG 814 has two LCs, LC#8 and LC#9. Each LCG has acorresponding LCG buffer. LCG 811 has LCG#1 buffer 821. LCG 812 hasLCG#2 buffer 822. LCG 813 has LCG#3 buffer 823. LCG 814 has LCG#4 buffer824. Further, each LCG buffer has a corresponding buffer status. LCGbuffer 821 has LCG#1-buffer status 831. LCG buffer 822 has LCG#2-bufferstatus 832. LCG buffer 823 has LCG#3-buffer status 833. LCG buffer 824has LCG#4-buffer status 834. An independent function entity for BSRhandling 841 of UE 801 handles BSR procedures for UE 801. BSR handler841 controls a MAC entity 851 and a MAC entity 852, which are associatedto BS 802 and BS 803, respectively. MAC entity 851 and MAC entity 852each has its own BSR handling functions. It is understood by one ofordinary skills in the art that more two MAC entities can be configuredto communicate with multiple base stations. BSR handler 541 controls themultiple MAC entities in similar manners.

In the hybrid BSR configuration, a retransmission timer is used by BSRhandler 841 to control the BSR reporting behavior. At the same time, MACentity 851 and MAC 852 is configured with a periodic timer. The value ofthe periodic timer for each MAC entity can be configured and/or dynamicchanged. The periodic timer for each MAC entity can be the same ordifferent. If the UL resources allocated for new transmission aregranted from any BS, all BSR triggers, either by BSR handler 841 or byeach MAC entity, should be considered to determine whether BSRs shouldbe cancelled. If the UL grants in the current subframe can accommodateall pending data available for transmission but is not sufficient toaccommodate the BSRs, the BSRs triggered by the corresponding MAC entityand by BSR handler 842 should be cancelled while the BSRs triggered byother MAC entities should not be affected. UE 801 monitors and detectsBSR trigger events. If MAC entity 851 or BSR handler 841 determines BSRreporting is needed, at step 861, UE 801 sends a BSR to BS 802. At step862, BS 802 replies to UE 801 with UL grants. If MAC entity 852 or BSRhandler 841 determines BSR reporting is needed, at step 863, UE 801sends a BSR to BS 803. At step 864, BS 803 replies to UE 801 with ULgrants.

In one embodiment, a BSR is triggered by BSR handler 841 if higherpriority data arrives or the BSR retransmission timer expires. A BSR istriggered by a corresponding MAC entity if the BSR periodic timerexpires or padding spaces becomes available to accommodate the BSR.

FIG. 9 is a flow diagram of a UE transmitting BSR to multiple basestations using hybrid BSR. At step 901, the UE determines if highpriority data arrived. If step 901 determines yes, the UE moves to step911 to set the BSR trigger by BSR handler 841. If step 901 determinesno, the UE moves to step 902. At step 902, the UE determines if the BSRretransmission timer expired. If step 902 determines yes, the UE movesto step 911 to set the BSR trigger by BSR handler 841. If step 902determines no, the UE moves to step 903. At step 903, the UE determinesif the BSR periodic timer expired. If step 903 determines yes, the UEmoves to step 912 to set the BSR trigger by a corresponding MAC entity.If step 903 determines no, the UE moves to step 904. At step 904, the UEdetermines is there is padding space available to accommodate the BSR.If step 904 determines yes, the UE moves to step 9112 to set the BSRtrigger by a corresponding MAC entity. If step 904 determines no, the UEterminates the procedure.

BS Selection

When a UE is configured with inter-base station carrier aggregation, theUE needs to select which base station to send the BSR. In general, ifthe UL resources allocated for new transmission are granted from one BS,the BSR will be transmitted to the BS that grants the UL resource. Ifthe UL resources allocated for new transmission are granted from morethan one BS, there are several methods to send the BSR.

In one embodiment of the current invention, one base station is selectedto receive the BSR. The criteria to select the base station may includethe base station responsible for a traffic loading, the base stationhaving better channel quality, the base station to which a schedulingrequest has been transmitted, and the base station granting the ULresources that can accommodate BSR with full buffer status information.Upon selecting a base station to transmit the BSR, the UE calculatingthe buffer status value for the BSR reporting.

FIG. 10 is an exemplary flow diagram of a UE calculating the bufferstatus value for BSR in accordance with embodiments of the currentinvention. At step 1001, the UE determines if the PDUs that wouldaccommodate the BSR can be generated by more than one MAC entities. Ifstep 1001 determines yes, the UE moves to step 1002. At step 1002, theUE select one base station to send the BSR report and moves to step1003. If step 1001 determines no, the UE moves to step 1003 directly. Atstep 1003, the UE calculates the buffer size value for each LCG afterall MAC PDUs have been built for this TTI. At step 1004, the UEdetermines the buffer status value based on the buffer size value foreach LCG.

In one novel aspect of the current invention, BSRs are sent to differentbase stations. In one embodiment, the BSRs are sent to different basestations with the same contents, where each LCG reports one bufferstatus value TTI. This buffer status value is the same for all BSRsreporting for the same LCG. In another embodiment, the BSRs are sent todifferent base stations with different contents.

FIG. 11 is an exemplary flow diagram of a UE calculating buffer statusvalue for separate BSRs to different base stations with the samecontents. At step 1101, the UE selects one or more BSs for BSR reportingwhich has granted UL resources that can accommodate the BSR. At step1102, the UE calculating the buffer size value for each LCG after allMAC PDUs have been built for this TTI. At step 1103, the UE determinesthe buffer status level based on the buffer size value for each LCG.

In other embodiments, the UE builds different buffer status values forthe selected different base stations. In one embodiment, each LCGreports at most one buffer status value per TTI. Different LCG mayreport different buffer status values. The buffer status value of eachLCG is reported in all BSRs containing this LCG to the corresponding BS.For example, assuming there are four LCGs available at the UE side,LCG1, LCG2, LCG3 and LCG4 and two BSs are configured to provide serviceto the UE. BS1 is responsible for UL resource allocation of LCG1 andLCG2, while BS2 is responsible for UL resource allocation of LCG3 andLCG4. BSR for LCG1 and LCG2 will be reported to BS1, and BSR for LCG3and LCG4 will be reported to BS2.

In another embodiment, the BSR reports to different base stations havedifferent contents. Each LCG can report more than one buffer statusvalue per TTI. The sum of the values for each LCG reflects the overallbuffer status of the LCG after all MAC PDUs have been built for thisTTI. The buffer status value for each LCG is split into several partsand sent to different base stations. In one embodiment, the sum ofbuffer status value for each LCG is split according to a preconfiguredload ratio among different BSs.

FIG. 12 is an exemplary flow diagram of a UE calculating buffer statusvalue for separate BSRs to different base stations with the differentcontents based on load ratio among different BSs. At step 1201, the UEcalculates the buffer size value for each LCG. At step 1202, the UEdetermines if the PUD that can accommodate the BSR can be generated bymore than one MAC entities. If step 1202 is no, the UE moves to step1203 to determine the buffer status level based on the buffer size valuefor each LCG and ends the procedure. If step 1202 is yes, the UE movesto step 1204 to weigh the buffer size value for each LCG with the loadratio configured for different BSs. The UE then moves to step 1205 todetermine the buffer status level based on the weighted buffer sizevalue for each LCG per base station.

Other ways to split the buffer status value for each LCG is based on theconfigurations of LCs and LCGs. Using this method, the LCs in each LCGare partitioned into several sets without overlapping. The BSRscorresponding to different BSs embody the total buffer status of eachpartitioned LC set. For example, LCG 1 contains LC1, LC2, LC3 and LG4.When BSR can be reported to BS1 and BS2 in the same TTI, BSR for LCG1considering LC1 and LC2 can be reported to BS1 and BSR for LCG1considering LC3 and LC4 can be reported to BS2. If the number of paddingbits in a PDU can only accommodate partial of the buffer statusinformation, the contained BSR will not provide full buffer statusinformation to the network.

Budget BSR

In one novel aspect, budget BSR is used to provide BSR reports to one ormore selected base stations. Initially, UE transmits UL data to only oneeNB/base station. The BSR is provided to the eNB/base station for ULscheduling. The Budget BSR enables the UE to inform a different eNB whenthe UL load budget on the original eNB has reached its limit and more ULradio resources are required. For example, when the total amount of ULdata or UL data for a logical channel in a LCG available fortransmission reaches a predefined threshold, the Budget BSR istriggered. The UE reports the event to a different eNB. In oneembodiment, the UE only reports the relative buffer status value,indicating the difference between the current buffer status and the BSRbudget. A periodic timer and a retransmission timer are used to controlthe budget BSR reporting behavior. In one example, the normal BSR isperformed by one MAC entity while the Budget BSR is performed by anotherMAC entity.

FIG. 13 is an exemplary flow diagram of a UE providing BSR and BudgetBSR to different base stations with separate MAC entities based on BSRand Budget BSR triggering and reporting. At step 1301, the UE monitorslayer two buffers. At step 1302, the UE detects the occurrence of one ormore predefined conditions. At step 1303, the UE determines if a BudgetBSR triggering event occurred. If step 1303 determines no, the UE movesto step 1304 to determine if a BSR triggering event occurred. If step1304 determines no, the UE moves back to step 1302 to monitor anddetermine is one or more predefined conditions are met. If step 1304determines yes, the UE moves to step 1306 and triggers regular BSR. Ifstep 1303 determines yes that a Budget BSR triggering event occurred,the UE moves to step 1305 to perform a Budget BSR.

Once a Budget BSR process is triggered, the UE performs the budget BSRprocedures similar to the process laid out in FIG. 4. The steps for aBudget BSR may include calculating the available space of thetransmitting PDUs based on the allocated UL resources, determiningwhether the available space of the PDUs to be transmitted canadditionally accommodate the Budget BSR, calculating the relative bufferstatus for each LCG after all MAC PDUs have been built for this TTI,selecting the PDUs in which the Budget BSR will be included, instructingthe Multiplexing and Assembly procedure to generate the PDU(s) forBudget BSR, transmitting the PDU(s) containing Budget BSR to the BS,starting or restarting Budget BSR periodic timer when all the generatedBudget BSR can provide full buffer status information, starting orrestarting Budget BSR retransmission timer, and cancelling all triggeredBudget BSRs in the corresponding MAC entity. If the UL grant(s) receivedby the MAC entity in this subframe can accommodate all pending dataavailable for transmission but is not sufficient to additionallyaccommodate the Budget BSRs, all triggered Budget BSR by the MAC entityand the BSR triggered by the independent function entity shall becancelled. The Budget BSR procedure follows the steps for a regular BSRas in FIG. 4. For Budget BSR, a base station is selected first toreceive the Budget BSR report. Therefore, the Budget BSR is performed bythe corresponding BSR handling entity based on the selected base stationto receive the Budget BSR.

In one embodiment, the Budget BSR is triggered when one or morepredefined UL data condition of is satisfied. The predefined conditionsmay include (a) the total amount of UL data for all logical channelswhich belong to the LCGs becomes available for transmission in the RLCentity or in the PDCP entity reaches to certain threshold, (b) UL data,for a logical channel which belongs to a LCG, becomes available fortransmission in the RLC entity or in the PDCP entity reaches to certainthreshold, (c) the total amount of UL data for a LCGs becomes availablefor transmission in the RLC entity or in the PDCP entity reaches tocertain threshold, (d) the total amount of UL data for all logicalchannels which belong to the LCGs becomes available for transmission inthe RLC entity or in the PDCP entity has reached to certain thresholdfor a period of time, (e) UL data, for a logical channel which belongsto a LCG, becomes available for transmission in the RLC entity or in thePDCP entity has reached to certain threshold for a periodic of time, and(f) the total amount of UL data for a LCG becomes available fortransmission in the RLC entity or in the PDCP entity reaches to certainthreshold for a period of time. The Budget BSR may also triggered if theBudget BSR retransmission timer expires, or the Budget BSR periodictimer expires, or there is padding space available in any UL sharedchannel (UL-SCH) through the Budget BSR MAC entity. The values of theperiodic timer and retransmission timer can be redefined orpreconfigured. The Budget BSR triggering threshold value can bepredefined or preconfigured as well. The values for these parameters,the timers and the threshold, can be configured or defined to be samefor all MAC entities or be different. It is understood by ordinaryskills in the art that the UE monitors and detects predefined conditionsto determine whether to trigger a budget BSR procedure. Forimplementations, the logic in the UE can check the Budget BSR conditionsfirst. If budget BSR conditions are not detected, the UE moves on tocheck regular BSR conditions.

FIG. 14 is an exemplary flow diagram of a UE triggering a Budget BSR inaccordance with embodiments of the invention. At step 1401, the UEdetermines if an predefined UL data condition reaches a predefinedthreshold as discussed above. If step 1401 determines yes, the UE movesto step 1411 to set the Budget BSR trigger. If step 1401 determines no,the UE moves to step 1402. At step 1402, the UE determines if the BudgetBSR retransmission timer expired. If step 1402 determines yes, the UEmoves to step 1411 to set the Budget BSR trigger. If step 1402determines no, the UE moves to step 1403. At step 1403, the UEdetermines if the Budget BSR periodic timer expired. If step 1403determines yes, the UE moves to step 1411 to set the BSR trigger. Ifstep 1403 determines no, the UE moves to step 1404. At step 1404, the UEdetermines is there is padding space available to accommodate the BSR.If step 1404 determines yes, the UE moves to step 1411 to set the BSRtrigger. If step 1404 determines no, the UE terminates the procedure.

To further reduce overhead of the BSR reporting and make the system moreefficient, no-data-indication is sent to signal the network. Theno-data-indication procedure is triggered if one or more predefinedconditions are met. The predefined conditions include the amount of dataavailable for transmission is below a threshold, the amount of datatransmission is below a threshold for a period, and the last byte of thedata available for transmission is transmitted. In general, when the UEexpects no data or only a small amount of data for transmission, or fora period of time only a certain amount of small data is available fortransmission, the UE sends an indication to one or more base stationssuch that no UL grants is needed. The indication can be sent through RRCsignaling, MAC CE, such as zero BSR on UL-SCH, or through UCI on PUCCH.

FIG. 15 is an exemplary flow diagram of a UE sending ano-data-indication to one or more base stations in accordance withembodiments of the current invention. At step 1501, the UE monitorslayer two buffer. At step 1502, the UE detects one or more predefinedconditions. At step 1503, the UE determines if one or moreno-data-indication trigger events occurred. If step 1503 determines no,the UE moves back to step 1501 to continue monitor the layer two buffer.If step 1503 determines yes, the UE moves to step 1504. At step 1504,the UE triggers the no-data-indication procedure. At step 1505, the UEtransmits a no-data-indication to the network.

FIG. 16 is a flow diagram of a UE selecting one or more base station tosend one or more BSR reports in accordance with embodiments of thecurrent invention. At step 1601, the UE calculates a buffer status valueby a UE in a multi-carrier wireless network with inter-base stationcarrier aggregation (CA), wherein the UE is configured with multiple LCsthat belong to one or more LCGs. At step 1602, the UE detects a BSRtriggering event. At step 1603, the UE selects one or more base stationsfor one or more BSR reports, wherein the UE receives uplink (UL)resource grants for a new transmission from multiple base stations. Atstep 1604, the UE generates one or more BSR reports for the selected oneor more base stations. At step 1605, the UE transmits the one or moreBSR reports to the selected one or more base stations.

FIG. 17 is a flow diagram of a UE performs Budget BSR procedure inaccordance with embodiments of the current invention. At step 1701, theUE calculates a buffer status value by a UE in a multi-carrier wirelessnetwork with inter-base station carrier aggregation (CA), wherein the UEis configured with multiple LCs that belong to one or more LCGs. At step1702, the UE detects a budget BSR trigger event or a BSR trigger event.At step 1703, the UE generates a BSR report and transmitting the BSRreport to a first base station upon detecting a BSR trigger event,wherein the first base station provides UL grants to the UE. At step1704, the UE generates a budget BSR report to a second base station upondetecting a budge BSR trigger event, wherein the budget BSR reportinforms the second base station more UL resources are required.

Avoiding Resource Over-Allocation

Since multiple schedulers residing in different eNBs are responsible forthe UL radio resource allocation to a UE, the schedulers performs the ULscheduling in a relatively independent way assuming that very infrequentand limited information related to the UE buffer status would beexchanged between them. After UE reports it buffer status to onescheduler, it is very likely that UL grants will be received from otherschedulers before the reported BSR is responded by the correspondingscheduler. So the reported BSR is actually out-dated. Currently, UEdoesn't have any opportunities to update its buffer status informationto the scheduler if other UL grants are received from other schedulerslater on. So the case of over-allocation of UL radio resources willoccurs very frequently due to the lack of non-updated buffer statusinformation.

One optimized method is that a variable for each scheduler is used whichholds the value of the data amount which has not been satisfied by thescheduler based on the reported BSR. It serves as the data amount, whichis expected to be transmitted through the UL resources after a BSR, hasbeen reported. The variable corresponding to a scheduler is thedifference between the reported BSR and the data amount, which has beenaccommodated by the UL radio resources granted. When a BSR is reported,the variable is replaced by the latest BSR value reported. It is updatedwhenever a UL grant is received from the scheduler and certain amount ofbuffered data is transmitted. It is updated to value for remaining datawhich has been satisfied by the scheduler. In this invention, thevariable for each scheduler is named as UDA (Unsatisfied data amount).

It is possible that even a BSR is reported to a scheduler, the dataamount can't be satisfied by the scheduler due to some reasons, e.g.lack of UL radio resources. In order to avoid UE waiting for the ULgrants from the scheduler and making the reported data amount stuck inthe buffer for a long period, a timer is used to control how long the UEconsiders the reported BSR should be satisfied by the scheduler. Thevariable corresponding to a scheduler is set to zero upon expiry of thetimer. The timer is started or re-started upon transmission of a new BSRexcept when all the generated BSRs are Truncated BSRs. In one embodimentof this invention, the method of BSR calculating and reporting comprisesthe following steps, assuming the number of schedulers is N. UDA_(i)stands for the unsatisfied data amount corresponding to the scheduler i;BS_(i) stands for the buffer size, which will be reported to thescheduler i; UGA_(i) stands for the amount of data which is availablefor transmission in the Layer two buffer and will be accommodated by theUL grants received from scheduler i; CBS, i.e. current buffer sizestands for the buffer size after all MAC PDUs have been built for thisTTI. i=0, 1 . . . N−1

-   -   Step one: Initialize UDA_(i)=0, BS_(i)=0;    -   Step two: When UL grant(s) are received from scheduler i,        calculate UGA_(i), and update UDA_(i) to        UDA_(i)=UDA_(i)−UGA_(i), and if UDA_(i)<=0, set UDA_(i) to 0;    -   Step three: When BSR has been triggered and would be generated        and reported to scheduler i, calculate CBS and BS_(i) where

${{BS}_{i} = {{CBS} - {\sum\limits_{{j = 0},{j \neq i}}^{N - 1}{UDA}_{j}}}};$

-   -   Step four: Update UDA_(i)=BS_(i);    -   Step five: Report BSR to scheduler i based on BS_(i).    -   Step six: Start or restart the timer corresponding to scheduler        i.        If the UL resources allocated for new transmission are granted        from more than one BS, there are several methods to deal with        the case. One method is that UE selects one scheduler to which        the BSR is reported. So step three is performed directly, so

${BS}_{i} = {{CBS} - {\overset{N - 1}{\sum\limits_{{j = 0},{j \neq i}}}{{UDA}_{j}.}}}$

One method is that UE reports multiple BSRs to different schedulersrespectively. So the BS value to each scheduler is calculated based on

${BS}_{i} = {{CBS} - {\overset{N - 1}{\sum\limits_{{j = 0},{j \neq i}}}{UDA}_{j}}}$

FIG. 18 is an exemplary flow diagram of a UE transmitting BSRs todifferent BSs implementing avoidance of radio resource over-allocation.After inter-eNB is configured for the UE and UE is ready for UL datatransmission to the activated serving cells originating from differenteNBs, UE begins to monitor PDCCH for UL resource allocation granted fromdifferent eNBs and performs UL data transmission accordingly. At step1801, the UE first initializes the variables UDA_(i), BS_(i) to zero foreach scheduler. At step 1802, the UE receives UL grants from multipleschedulers. At step 1803, the UE determines if UL grants are received.If step 1803 determines no, the UE moves back to step 1802. If step 1803determines yes, the UE moves step 1804 and determines from whichscheduler each UL grants are received. At step 1805, based on the ULgrants, the UE calculates the amount of data that is available fortransmission in the UL buffer and can be accommodated by the UL grantsreceived from each scheduler, i.e. UGA_(i). At step 1806, the UE checkswhether the timer expires or not. If the timer expires, the UE moves tostep 1807, where UDA_(i) is set to zero. Then UE moves to step 1808 andupdates UDA_(i) to UDA_(i)−UGA_(i) for each scheduler where UL grant(s)are received. If step 1806 determines that the timer did not expire, theUE moves to step 1808 directly and updates UDA_(i) to UDA_(i)−UGA_(i)for each scheduler where UL grant(s) are received. At step 1809 the UEdetermines if UDA_(i)<=0, If step 1809 determines yes, the UE, at step1810, sets UDA_(i) to be zero and moves to step 1811. If step 1809determines no, the UE moves to step 1811 directly. At step 1811, the UEdetermines if the UL grants are received from only one scheduler. Ifstep 1811 determines yes, the UE moves to step 1812 to determine whetherBSR has been triggered for it. If step 1812 determines that BSR has beentriggered, the UE will move to step 1816 to prepare to report BSR to thescheduler. If step 1812 determines no, the UE moves back to step 1802.If step 1811 determines that UL grants are received from more than onescheduler, the UE moves to step 1813 to determine whether multiple BSRsintended to only one scheduler where UL grants are received have beentriggered respectively. If step 1813 determines no, the UE moves to step1814. At step 1814, the UE determines if multiple BSRs are for differentschedulers. If so, the UE selects one scheduler to which BSR will bereported. Otherwise, UE will report BSR to the scheduler for which BSRhas been triggered. After UE determines to which scheduler the BSR willbe reported, the UE moves step 1816 to prepare to report the BSRs. Atstep 1816, the UE calculates current buffer status after all MAC PDUshave been built in the TTI. Then at step 1817, the UE calculates BS_(i)for the scheduler, which equals to

${BS}_{i} = {{CBS} - {\overset{N - 1}{\sum\limits_{{j = 0},{j \neq i}}}{{UDA}_{j}.}}}$

At step 1818, the UE updates UDA_(i) to BS_(i). At step 1819, the UEdetermines the buffer status. At step 1820, the UE reports BSR to thescheduler based on the value of BS_(i). At step 1821, the UE starts orrestarts the timer. At step 1822, the UE determines if UL transmissioncontinues. If step 1822 determines yes, the UE moves back to step 1802.If step 1822 determines no, the UE terminates the procedure.

Although the present invention has been described in connection withcertain specific embodiments for instructional purposes, the presentinvention is not limited thereto. Accordingly, various modifications,adaptations, and combinations of various features of the describedembodiments can be practiced without departing from the scope of theinvention as set forth in the claims.

What is claimed is:
 1. A method comprising: calculating a buffer statusvalue by a user equipment (UE) in a multi-carrier wireless network withinter-base station carrier aggregation (CA), wherein the UE isconfigured with multiple logical channels (LCs) that belong to one ormore logical channel groups (LCGs); associating a first MAC entity witha first base station; associating a second MAC entity with a second basestation; detecting a buffer status report (BSR) triggering event;selecting one or more base stations of the first base station and thesecond base station for more BSR reports, wherein the UE receives uplink(UL) resource grants for a new transmission from one or more basestations of the first base station and the second base station;generating one or more BSR reports for the selected one or more basestations; and transmitting the one or more BSR reports to the selectedone or more base stations.
 2. The method of claim 1, wherein one basestation is selected to receive the one or more BSR reports, and whereinthe base station is selected based one or more criteria comprising: thebase station is responsible for traffic offloading, the base station hasbetter channel quality than a threshold, the base station receivesscheduling request (SR) before, and the base station grant UL resourcesthat can accommodate the full buffer status requirement by the UE. 3.The method of claim 1, wherein more than one base stations are selectedto receive BSR reports.
 4. The method of claim 3, wherein the same BSRreport is generated for all base stations from which the UE receives ULgrants.
 5. The method of claim 3, wherein different BSR reports aregenerated for different base stations from which the UE receives ULgrants.
 6. The method of claim 5, wherein multiple BSR reports aregenerated for each LCG to be sent to different base stations, andwherein the full buffer status value for the LCG is split to themultiple BSR reports according to a predefined or preconfigured loadratio of corresponding base stations.
 7. The method of claim 5, whereinmultiple BSR reports are generated for each LCG, and wherein each BSRreport is generated for a preconfigured non-overlapping subset of LCs ina LCG, and wherein each preconfigured subset of LCs relate to the samebase station.
 8. The method of claim 1, further comprising: updating thebuffer status value upon receiving a UL grant or a portion of buffereddata is transmitted.
 9. The method of claim 1, wherein the triggeringevents comprising: arrival of high priority data, expiration of aperiodic timer for BSR, UL data amount reaches a predefined threshold,expiration of a BSR retransmission timer, and padding space in a PDUbecomes available.
 10. A user equipment (UE) comprising: a radiofrequency (RF) transceiver that transmits and receives radio signalsfrom multiple base stations in a wireless network; a first MAC entity,wherein the first MAC entity is associated with a first base station; asecond MAC entity, wherein the second MAC entity is associated with asecond base station; a processor, that calculates a buffer status valueof the UE, the UE is configured with multiple logical channels (LCs),wherein multiple logical channels (LCs) that belong to one or morelogical channel groups (LCGs), and wherein at least a first LC relatesto the first base station and at least a second LC relates to the secondbase station; detects BSR trigger events; that selects one or more basestations for one or more BSR reports, wherein the UE receives ULresource grants for a new transmission from the one or more basestations; and a BSR generation module that generate one or more BSRreports.
 11. The UE of claim 10, wherein the processor selects one basestations for a BSR reporting.
 12. The UE of claim 10, wherein theprocessor selects multiple base stations for a BSR reporting.
 13. The UEof claim 12, wherein the same BSR report is generated for all the basestations from which the UE receives UL grants.
 14. The UE of claim 12,wherein different BSR reports are generated for different base stationsfrom which the UE receives UL grants.
 15. The UE of claim 13, wherein aBSR report is generated by the BSR generation module independent of thefirst MAC entity and the second MAC entity.
 16. The UE of claim 13,wherein two BSR reports are generated by the BSR generation module, andwherein a first BSR is associated with the first MAC entity and a secondBSR is associated with the second MAC entity.
 17. The UE of claim 10,wherein one or more BSR reports are generated by the BSR generationmodule if the BSR detection module detects trigger events comprises:expiration of BSR periodic timer relating to the first or the second MACentity, and padding space is available in the PDU relating to the firstor the second MAC entity.